@Teun11
To leave a review, first you have to go through the rigmarole of setting up an account then actually have to book the listing. I'm sure there are a few fake reviews out there, but in general if you looked at a few random listings you get a fast feel for authenticity. Probably more destructive competitor reviews than puffed up boosterism reviews exist.
SpB attracts lots of visitors, especially during the White Nights high season, so there is a buoyant market of places to rent.
As a student in SpB you should prepare a checklist to fit your needs - near transport links, especially metro, place inside a yard rather than looking over a busy street with trams clanking by from 5am, away from communalka flats, communal skips or 24hr stolovaya canteens or K&B off licenses.
Also to decide historic central area vs new builds further out of the city...